MFS r341146
MFC r340994
Prevent kernel stack disclosure in getcontext/swapcontext
Expand r338982 to cover freebsd32 interfaces on amd64, mips, and powerpc.
Approved by: re (gjb)
Security: FreeBSD-EN-18:12.mem
Security: CVE-2018-17155
Sponsored by: Dell EMC Isilon